Dogs and other canids are affected by a number of diseases against which it would be desirable to develop protective vaccines. Live vaccines, and particularly live viral vector vaccines, are attractive vaccine vector candidates as they appear to be associated with longer-lasting immunity than inactivated virus vaccines or subunit vaccines. One disadvantage of live vaccines, however, has been that attenuated virus strains often revert to virulence. Another disadvantage has been the host range of a number of viral vaccines. In an attempt to deliver genes to an animal, several viral and bacterial systems, such as poxviruses, adenoviruses, Salmonella, and BCG (Bacillus Calmette-Guerin), have been genetically manipulated to generate vectors containing heterologous antigen genes in order to immunize a host with a vaccine in which the antigens are presented in a "live" configuration. See, for example, the following two review articles: Esposito et al., pp. 195-247, 1989, Advances in Veterinary Science and Comparative Medicine, Vol. 33; Dougan et al., pp. 271-300, 1989, Advances in Veterinary Science and Comparative Medicine, Vol. 33.
Several herpes virus vaccines, such as those based on bovine herpes virus (BHV), cytomegalovirus (CMV), Epstein Barr virus (EBV), equine herpes virus (EHV), feline herpes virus (FHV), herpes simplex virus (HSV), Marek's disease virus (MDV), pseudorabies virus (PRV), turkey herpes virus (HVT), and varicella zoster virus (VZV) have been developed and several have shown at least some efficacy as vaccines against the virus per se or as vectors carrying other genes in certain indications. The listed herpes viruses, however, also have the drawback that even if attenuated, they are subject to reversion.
Canine herpes virus (CHV) infection is a relatively benign infection except in newborn puppies. A few vaccines to protect against CHV infection have been reported including a small-plaque variant CHV vaccine disclosed in U.S. Pat. No. 4,213,965, by Carmichael, issued Jul. 22, 1980. The nucleotide sequences of CHV genes encoding gB, gC, gD and UL45 homologs have been reported by Limbach et al., 1994, J. Gen. Virol. 75, 2029-2039, but these proteins, while proposed as vaccine candidates against CHV, were not tested as such by Limbach et al., ibid.
The inventors are not aware of any reports which describe the use of CHV as a vaccine vector, either with respect to inactivating genes in the CHV genome using recombinant DNA techniques, and/or to delivering protective compounds to a canid, in spite of the need to develop safe and efficacious delivery systems to protect canids, and especially dogs, from disease. Two U.S. patents (i.e., U.S. Pat. No. 5,266,489, by Rey-Senelonge et al., issued Nov. 30, 1993; and U.S. Pat. No. 5,223,424, by Cochran et al., issued Jun. 29, 1993) at best speculate on the insertion of genes into certain CHV loci, but neither claims CHV vectors or vaccines, nor provides data supporting such speculations. U.S. Pat. No. 5,266,489, ibid., claimed HVT having a foreign gene inserted into the ribonucleotide reductase (RR) small subunit gene of the HVT genome, but also disclosed without support the insertion of foreign genes into the RR small subunit genes of BHV, CHV, CMV, duck herpes virus, EBV, EHV, FHV, HSV, PRV and VZV. The inventors, however, have demonstrated the inaccuracy of this disclosure in that the inventors have found, and disclosed in the present application, that the CHV genome lacks the RR small subunit gene. That is, the CHV RR small subunit gene does not exist to provide a target for the insertion of foreign genes.
U.S. Pat. No. 5,223,424, ibid., claimed specific hybrid PRV constructs having deletions in the TK, repeat, or and/or gX regions and heterologous sequences inserted into the repeat and/or gX regions, but also proposed without data the ability to insert foreign genes into the repeat region of the CHV genome, even though that genome had not yet been mapped. Also disclosed were certain BHV and HVT constructs and proposals, without data, to delete and insert genes in other herpesviruses, such as EHV and FHV, HSV and MDV. It is also of note that a patent application (now U.S. Pat. No. 5,273,876, by Hock et al, issued Dec. 28, 1993) that was filed significantly later than U.S. Pat. No. 5,223,424, ibid., and shares two co-inventors with U.S. Pat. No. 5,223,424, ibid., states in column 2, lines 57-61, "Among the herpesviruses, only four herpesviruses (herpes simplex of humans, herpes saimiri of monkeys, pseudorabies virus and varicella-zoster virus) have been engineered to contain foreign DNA sequences previous to this disclosure," thereby indicating the lack of CHV, or a number of other, herpes virus vectors.
Thus, there remains a need for new and improved methods to vaccinate canids to protect them from diseases, such as those caused by genetic or metabolic disorders as well as those caused by infectious agents such as protozoan parasites, helminth parasites, ectoparasites, fungi, bacteria, and viruses.